This invention relates generally as indicated to a reinforcing bar splice and method, and more particularly to a low cost concrete reinforcing bar splice for use in steel reinforced concrete construction. The splice is designed to be cost competitive to a conventional lap splice, yet providing a substantially superior splice both in tensile and compressive strength and dynamic or fatigue strength capabilities.
In steel reinforced concrete construction, there are generally three types of bar splices employed. There are lap splices, mechanical splices, and welding. Each has advantages and disadvantages. Perhaps the lowest cost and most commonly used splice is the lap splice. The lap splice is normally formed by overlapping bar ends to be joined and wire-tying the side-by-side overlapped ends to each other. Some lap splices are formed with the bars laterally spaced. The extent of the side-by-side overlap may be substantial, requiring additional significant reinforcing steel. Also since the bars are axially offset, any load whether compressive or tensile is going to be eccentric. Lap splices also create forming and design problems because the axes of the joined bar are offset. For the same size bar, the joint will be at least as wide as two overall diameters of the bars, which are greater than the nominal diameters of the bars. Each bar is then at a different lateral spacing from the form. Thus, in order to obtain minimum concrete cover for the beam, slab, or column, for example, the form size and structure may be larger than it needs to be. It would accordingly be desirable if a low cost easily installed equivalent of a lap splice joint could be formed where the bars joined are axially aligned end-to-end.
It would also be desirable to be able to enhance the splice not just effectively to correct the disadvantages of lap splices, but also to provide a splice having superior strength characteristics in both compression and tension, but which will also meet dynamic or fatigue requirements to be a Type 2 coupler or splice where use is permitted in any of the four (4) earthquake zones of the United States. It would of course be desirable to enhance the splice without additional significant cost and without preparation or treatment of the joined bar ends such as with an upset or threaded ends found in many mechanical splices.
A bar splice for steel reinforced concrete construction utilizes a cage of relatively short reinforcing bars which may be of smaller size than the bars to be joined. The bars of the cage are secured together and arranged in a circular cylindrical fashion with an axial center opening designed to receive the axially aligned bar ends to be joined. The bars of the cage may be joined in a parallel circumferentially spaced cylinder by one or more rings or wires, and the cage is clamped to the bar ends by clamp or set screws threaded in nuts secured to the rings. The bar end is clamped between the set or clamp screw tips and the opposite side of the cage. The splice may be used for both horizontal and vertical or column joints. When the concrete is poured it embeds the cage and axially aligned bar ends, locking the bars axially end-to-end.
In a modified or enhanced version of the splice, the cage is enclosed in a sleeve and the set or clamp screws are threaded through nuts or nut bars on the sleeve to clamp the bar ends against the inside of the cage which bridges or laps the bar ends within the sleeve. Before concrete is cast around the joint, the sleeve is filled with a hardenable matrix which embeds the cage and the bar ends. The matrix is preferably a hardenable resin, such as epoxy, or a grout which embeds not only the cage but the bar ends. The enhanced performance of the splice is achieved in part by the clamp or set screws, but also by the matrix embedding the cage and bar ends within the sleeve.
To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.